1. Field of the Invention
This invention generally relates to range safety devices and more specifically to a projectile backstop assembly using uncontained loose resilient particles, such as rubber.
2. Description of the Related Art
A number of backstop assemblies for slowing down projectiles, such as bullets or arrows, are known. Some contain granulated material. A typical container for such granulated material is a box-shape container with a self-healing medium dispersed across the side of entry of the projectile. For example, U.S. Pat. Nos. 5,171,020, 5,340,117, and 5,435,571, all to either Wojcinski or Wojcinski, et al. disclose box-shaped containers covered with a self-healing medium, such as rubber or sheets of polymer material with the required elasticity for self-healing.
The projectile enters the container through the self-healing medium but it is the granulate matter located within the container that largely slows down and captures the projectiles after they have entered the container. A disadvantage of the Wojcinski-disclosed backstop assembly is the cost of elements, such as the box-shaped container and the self-healing medium which provide little of the desired functionality of slowing down a projectile. Clearly, it would be economically advantageous to slow down projectiles without the need for such containment means, and particularly for disposing of the requirements of a box-shaped container or a medium covering the opening of such a box.
A further disadvantage of the above-disclosed systems is the need to use flowable granulant materials arranged so that the granulates are periodically moved downward through slopped walls in the bottom of the box that act like a hopper to remove them from the container. To flow the granulates a mechanical agitator or vibrating system is employed. Additionally, to reduce binding or fusing of the material, caused by factors such as the combined weight of the granulants on ones disposed below water is added to the container through a complicated pump system. The requirement of such systems as motorized vibrating means or pump activated water injecting means is very expensive. Thus, it would be an advancement of the art to provide projectile slowing down and capturing assemblies that do not require such machinery.
Other backstop assemblies requiring containers are disclosed by Wojcinski. One containerized backstop assembly is disclosed by Wojcinski in U.S. Pat. No. 4,683,688. The assembly is part of a containerized shooting range and it consists of two rows of louvered panels of hard rubber material. The louvered panels are generally contained within an integral box-shaped container and further within the walls of the shooting range container itself. Another projectile backstop assembly disclosed by Wojcinski in U.S. Pat. No. 4,817,960 includes a container filled with a liquid for decelerating a projectile and elongated sheet of materials sealing the inlet opening. Two other backstop assembles disclosed by Wojcinski in U.S. Pat. Nos. 4,458,901 and 5,040,802 each include a container housing a series of lamella within a frame. A disadvantage of the lamellas is the expense of creating the complex geometry and the need to replace the lamellas when those become damaged by a projectile.
Further contained systems for slowing down and catching projectiles such as bullets are disclosed in U.S. Pat. No. 4,819,946 to Kahler, U.S. Pat. No. 5,486,008 to Coburn, and U.S. Pat. No. 2,743,106 to Schels. The Kahler-disclosed device includes a box with a plurality of vertically oriented resilient panels, aligned with an opening of the box. The Coburn-disclosed device includes a deceleration chamber that relies on complicated geometry and liquid lubricants to slow down a bullet. The Schels-disclosed device provides a receptacle for catching low velocity, low weight projectiles from toy guns including a felt or fibrous fabric to cushion the impact of pellets. Each of the above-described projectile backstop assembles has a disadvantage of requiring a container in parts of complex geometry which must be periodically replaced.
U.S. Pat. No. 4,856,791 to McQuade describes a protective mat assembly that employs a sheet of elastomeric material and a cellular foam substrate mounted to a rigid panel. Projectiles which strike the assembly impact against the plate and projectile fragmentation is contained within the assembly. Although the McQuade-disclosed device does not require a box-shaped container, it has the disadvantage that it allows the projectile to fragment. When a projectile, such as a bullet fragments, it disperses its constituents. In the case of bullet, this means that lead is dissipated into lead dust which is a recognized environmental hazard. Shooting ranges that have backstop assemblies that allow fragmentation of the bullet must hire hazard treatment personnel to periodically remove the lead dust. This is very expensive. Thus it would be a clear advancement in the art to provide a low-cost backstop assembly which did not allow a projectile, such as a bullet to fragment.
It is known to layer strips or plates, one behind the other. One such arrangement is described in German patent publication DE3900-864 A1. The individual strips are inclined to define direction and may be turned over and slid mechanically to alter their angle to the firing direction and reversed over time. German patent publication DE4022-327 A1 shows a similar arrangement but the strips appear to be normal to the firing direction. In either case, the mats or strips must be periodically replaced and are expensive to manufacture and replace.
Clearly there is a need in the art for a low-cost backstop assembly that introduces no lead dust and requires no expensive lubricating or agitating equipment. Further, it would be advantageous to provide such a low-cost backstop assembly not requiring containing means or a projectile receiving medium separate from a medium used to slow and capture a projectile.